1. Field of the Invention
The present invention relates generally to a fixture for testing the shear strength of a longitudinal weld interconnecting two or more planar blanks forming a tailor weld blank.
2. Description of the Related Art
The desire to manufacture lighter-weight and lower cost vehicles has resulted in the automotive industry looking at alternative materials, other than steel, for manufacturing vehicle body structures. Aluminum is one such material because it has qualities such as low density, good mechanical properties and high corrosion resistance. Additionally, cost and weight can be saved with aluminum vehicle body structures with the use of tailor welded blanks. Tailor welded blanks include two or more sheets of material, such as aluminum, of dissimilar thicknesses and/or material properties which are joined together through some type of welding process. Tailor welded blanks eliminate the conventional need for reinforcement parts and stamping dies used to manufacture them, thus, reducing weight and cost. Additionally, tailor welded blanks are often stiffer than conventional reinforced structures, thus making it possible to down-gauge the material used in the blanks.
Welding of steel tailor welded blanks tends to increase the strength of the weld material which helps prevent failure along the length of the weld during forming, such as stamping. Aluminum tailor welded blanks, however, do not experience this increase in strength, and therefore, may have a greater tendency to fail along the length of the weld. Additionally, the gauge, or thickness, differential intrinsic to tailor welded blanks may result in strain localization during stamping of the aluminum structures. This strain localization along the length of the weld may potentially be more severe in aluminum because of its limited formability as compared to the typical drawing-quality steels. The dominant failure mode in tailor welded blanks is shear and therefore, it is desirable to provide a method and fixture for testing the shear strength of a tailor welded blank and quickly access the feasibility of a particular tailor welded blank for an aluminum vehicle body structure.
Accordingly, the present invention is a fixture for testing the shear strength of a generally longitudinal weld interconnecting at least two planar blanks forming a tailor welded blank. The fixture includes a first pair of face plates connected to one side of the planar blanks wherein each of the first pair of face plates includes a transverse edge extending across the longitudinal weld which connects each of the planar blanks. The fixture further includes a second pair of face plates connected to the opposing side of the planar blanks wherein each of the second pair of face plates includes a transverse edge extending across the longitudinal weld which connects each of the planar blanks. The fixture includes the transverse edges of the first and second pair of face plates having a first portion and a second portion spaced from and parallel to the first portion. The fixture also includes the transverse edges of the first and second pair of face plates having an isolation portion interconnecting the first and second portions for isolating a portion of the weld which connects each of the planar blanks whereby the portion of the weld is isolated for shear strength testing in response to a tensile load being applied to the first and second pair of face plates.
The present invention further includes a method of testing the shear strength of a longitudinal weld interconnecting at least two planar blanks forming a tailor welded blank. The method includes the step of forming a cut slit through each of the planar blanks terminating at a portion of the weld. The method further includes the step of positioning the tailor welded blank between a first and second pair of face plates. The method includes the step of aligning a transverse edge of each of the first and second pair of face plates with the respective cut slit in each of the planar blanks and aligning an isolation portion of the transverse edge adjacent and parallel with the portion of the weld extending between the cut slits. The method also includes the step of securing the tailor welded blank between the first and second pair of face plates with the transverse edges extending across each of the planar blanks. Finally, the method includes the step of applying a tensile load to the first and second pair of face plates and the tailor welded blank to test the shear strength of the portion of the weld extending between the cut slits and isolated between the isolation portions of the transverse edges of the first and second pair of face plates.
One advantage of the present invention is that a fixture and method is provided for testing the shear strength in tailor welded blanks. Another advantage of the present invention is that the fixture and method provides an easy method of testing a tailor welded blank""s resistance to shear loading and to quickly access the feasibility and formability of tailor welded blanks, particular for aluminum vehicle body structures.
Other features and advantages of the present invention will be readily appreciated as the same becomes better understood after reading the subsequent description when considered in connection with the accompanying drawings.